Production of bioconcrete with improved durability properties using Alkaliphilic Egyptian bacteria

Microbial-based self-healing of concrete represents innovative technology for improving micro-crack sealing. Microbial bioactivity can induce calcite-precipitation in concrete, which seals micro-cracks. In this respect, two Egyptian bacterial isolates were selected and identified, as Bacillus subtilis (Bs) and Bacillus megaterium (Bm) using MALDI-TOF/MS-Biotyper^®. Peak patterns of the bacterial ribosomal proteins showed a high match between samples and standards, which verified species consistency. Bs and Bm were added to the mortar mixture in two concentrations (0.5%, 1%) of cement weight, then the mechanical and physical properties were tested throughout a 180-day time course. The compressive strength of Bm0.5 bacterial mortar samples was increased by 21.4% after 28 days, as compared to control. The rate of water absorption of Bm samples was decreased by 12.4% after 180 days. Bacterial mortar samples showed significant restoration of compressive strength than the original samples by 44%, 21%, and 52.6% for Bs1, Bm0.5, and Bs0.5, respectively. SEM and EDAX analyses confirmed that bacterial samples were denser with fewer voids than the control, as a result of microbial nanosized calcite-precipitation. DTA verified that the amount of CaCO₃ and its degree of crystallinity were increased in the bacterial mortar samples. Load-deflection of reinforced-laminates for bacterial mortar samples showed ductile behavior and less deformation as compared to control. In this work, novel concrete with improved mechanical and physical properties has been developed using selected Egyptian microorganisms, it can promote self-healing of micro-cracks with improved durability of the concrete. The application of self-healing bioconcrete can reduce the inspection and maintenance costs.

The online version contains supplementary material available at 10.1007/s13205-021-02781-0.